Method of drilling wells



' Dec, 14,1937. J. G. Dvi-:R

METHOD OF DRLL'NG WELLS Filed July 2, 1936 $194' 3 Sheets-Sheet y L R.. @Pff mx J. 0 7, 6 J Y B um.

ATTORN EY Dec. 14, 1937. J. G. DYER 2,102,555

METHOD OF DRILLING WELLS Filed July 2, 1956 5 Sheets-Sheet 2 BYZJKW ATTORNEY Dec. 14, 1937. J. G. DYER 2,102,555

METHOD OF DRILLING WELLS Filed July 2, 1956 5 Sheets-Sheet 3 awr/ZM? ATTOR N EY Patented Dec. 14, 1937 UNITED STATES METHOD 0F nmLLlNG WELLS Joleph G. Dyer, Ponca City, Okla., assigner to Continental Oil Company, Ponca City. Okla., a corporation of Delaware Application July 2, 1936, Serial No.4 88,563

3 Claims Mv invention relates to a method ofdrilling wells and more particularly to drilling wells through layers of heaving shale. y

In undertaking development of areas for obtaining oil, great diiliculty is encountered in certain regions of south Texas where heaving shale is encountered in the Oligocene formation. Drilling through heaving shale, especially where it is of considerable depth, has baflled operators for years. Throughout the Gulf Coast fields, oil and gas are overlain by shales ofconsiderable thickness. Some of these cave badly. In places, the caving and associated movements assume such magnitude and force as to be termed heaving. Starting usually with a slight sloughing and caving, the trouble increases progressively until the rock movements attain force of great magnitude, such that 'they are impossible to control by any known method. Each heave grows more severe than the one preceding. At first, there is merely a tendency to stick the drill pipe in the hole and pack ofi circulation but, as the trouble becomes accentuated a single heave may close the hole or iill it for thousands of feet. When this occurs, drill pipe and casing are bent, twisted and broken. The junk left in the hole may never be found. In extreme cases, drill holes several thousand feet deep, enclosed nearly to the bottom, will be filled nearly to the surface with fragments of shale heaving from close to the bottom.` Such forces, once active, cannot be controlled.

'I'he formations which heave are composed of several kinds of shale interbedded with each other. Some have bentonitic characteristics which cause them to swell many times their initial volumes upon contact With water. Others merely disintegrate without swelling. This disintegration is caused principally by hydration.

In my co-pending application, No. 40,746, filed September 16, 1935, I have disclosed that continuous circulation of drilling mudwithout stopping while adding sections to the drill string would promote the drilling through heaving shale. The cessation of circulation frequently will cause the loss of the hole either through the sticking of the drilling string or the developing of heaves before the objective can be reached. One of the primary requisites in drilling through heaving shale, therefore, is speed in the operation.v

As pointed out, the heaving first starts with a slight sloughing and caving. If this is kept to a minimum, heaves of such magnitude as to destroy the hole can be prevented.

(Cl. Z-24) One of the methods of preventing heaving from developing so rapidly that heaves of large magnitude are reached is to employ chemicalmuds. With ordinary drilling muds composed of colloidal matter suspended in water, the walls 6 of the hole act as a filter. 'I'he water from the mud penetrates the formation, depositing a filter cake cf walling material. The water however, causes hydration of the shale, followed by disintegration and sloughing. Both, the shale and l0 the walling material are broken down progressively, thus exposing more shale to hydration.- This process is self-stimulating and `will develop heaving Within a short time, usually a few days after the initial penetration of the shale( I eml5 ploy sodium silicate drilling muds. Sodium silicate reacts with the shale to form insoluble, protective filmson all exposed surfaces. The shale is thus protected against hydration anddisin-l tegration. Suilicient mud viscosity to carry out 20 the cuttings, coated with protective silicates, is obtained through the addition of sodium bentonite. Weighting materials may be used to furnish additional weight so that the hydrostatic pressure of the column of drilling fluid will tend 25 to. prevent the collapsing of the hole from the Weight of the formations themselves.

One object of my invention is to provide a method of drilling oil wells through layers of heaving shale.

Other and further objects of my invention will appear from the following description.

In the accompanying drawings which form part of the instant speciiication and are to lbe read in conjunction therewith and in which like 35 reference numerals are used to indicate like parts in the various views;

Figure 1 is a diagrammatic cross sectional view of an oil well known as Moody No. 2-A, located near Seadrift, Calhoun County, Texas.

Figure 2 is a diagrammatic view of the rig in one stage of the drilling operations.

Figure 3 isa diagrammatic view of the rig in another stage of the operations.

Figure 4 is a diagrammatic view of the drilling 45 rig in another stage of the operations.

Figure 5 is an enlarged detail view with parts in section of a bit head containing a collapsible drilling bit, expanded for drilling.

Figure 6 is a view with parts in section of the 50 bit head and collapsible drilling bit with the blades in closed position for pulling out of the hole through the casing.

Figure 7 is a detail view partly in section of a quick acting joint.

Figure 8 is a sectional view taken on the line 8 8 of Figure 7.

Figurer is a sectional view of a valve joint with which continuous circulation is maintained.

My method can be best understood by describing it with reference to a particular well but it is to be understood that this is by way of example andv not by way of limitation.

The well shown diagrammatically in cross section in Figure 1 is a completed well drilled by the use of my method within 150 feet of a well previously lost by heaving. 'I'he heaving shale was encountered at 6150 feet, in the Discorbis, Heterostegina. and Marginulina formations of the Oligocene era which extended for 1600 feet.

The drilling was started with an ordinary rotary drill using the conventionallmethods and at 182 feet a 20 inch casing I was set and cemented at 2. Drilling, still by conventional methods, continued to 1475 feet and a 16 inch casing 3 was set and cemented at I. Drilling then continued, still by conventional methods, to about 6100 feet, within 50 feet of the beginning of the heaving shale. A casing 5, 11% inches in diameter,v was then `set and cemented at l, a thousand sacks of cement being used. Up until this point, the drilling presented no diiilculties and any conventional method of rotary drilling can be employed.

Heaving of shale does not occur until after i the heaving shale layer has been penetrated for some distance. The heaving shale has been penetrated for about 300 feet before departure from the conventional methods. This can always be gauged by watching the cuttings carefully and, when signs of caving are noticed it is unsafe to drill deeper and set the casing by conventional methods.

At the point of setting of casing 5, the problem was to drill through 1600 feet of heaving shale without losing the hole. In order to successfully accomplish this, the following objectives must be kept in mind:

l. Disintegration and swelling oi' the shale due to hydration by water from drilling muds must be minimlrnized.

2.The drilling must proceed with despatch to prevent aggravation of caving or heaving. 'I'his necessitates;

(a) Use of mechanical equipment enabling new sections of drill string to be added rapidly.

(b) The maintenance of continuous circulation even while adding sections to the drill string.

(c) A method of drilling in which it will not be necessary to pull the drill string to set a casing accomplished by the use of the casing itself as the drilling string and the use of a collapsible bit which can be withdrawn without disturbing the drilling string in order to convert the drilling string into a casing.

3. To prevent the action of gas blowing shale into the hole.

4. To prevent movement of shale caused by weight of overlying formations.

The action of gas blowing shale into the hole was prevented by the use of drill muds, the hydrostatic weight of which would hold back the gas, and the movement of shale caused by the weight of overlying formations was likewiseminimized by the use of drilling muds and by keeping the pipe in the hole and converting it into a casing.

To prevent disintegration and swelling of the shale by preventing hydration thereof, sodium silicate drilling muds were employed. Sodium silicate reacts with rock forming materials such -mediately develop forces of large magnitude and in many cases it is possible to wall the hole suf- Iflciently with ordinary muds to delay caving of such proportions as to lose the hole, if the drilling proceeds with sufficient rapidity. It is essential Aalways to maintain a continuous circulation. 'Ihis is done by means of a valve union such as shown in V1iigure9 in which a valve 1 is adapted to close an opening in the side of the union or an opening across the bore of the union depending on whether the ow is downwardly through the union or in through the side.

In order to insure rapidity of adding sections, a quick acting joint is employed such as shown in Figures 7 and 8. A male portion 9 of the quick acting joint is secured to the casing i at the top of the section. The male portion is provided with lugs il which are adapted to fit in the female portion i2 of the joint which is secured in any suitable manner to the bottom of a section of casing. 'I'he female portion is provided with grooves i3, aligned with the lugs Il. To make the joint, the grooves II are seated in the slots il and the male portion telescoped in the female portion of the joint. Hammer pins il are driven at right angles to the axis and lock the joint in telescoped position. The hammer pins taper so that, when they are driven the joint is drawn together. Safety pins I are fitted to prevent the hammer pins il from withdrawing. This joint has many advantages in making a quick connection. Stabbing may take place at an angle and it is not necessary to carefully start the thread as is the case with the usual connection so that connection work is speeded up considerably.

Figure 3 shows the assembly with drilling through the heaving shale ready to begin. The drill string is comprised of 8% inch casing. The bottom of the casing terminates in a bit head I6 in which a. collapsible bit I1 of any suitable construction is adapted to be seated. The bit head and collapsible bit are shown in Figures 5 and 6. In Figure 5 the bit is shown in extended position in the bit head I6 with the cutting blades i8 extended. In Figure 6 the bit is shown in collapsed position ready to be pulled out of the hole. The depth of heaving shale is known from geophysical data and, in this case, it was 1600 feet. 'I'he casing I 9 is assembled with usual casing joints for 1600 feet, at which point a back-01T joint 20 is inserted. The back-off joints are known to the art and consist merely of connections having'means to permit easy unscrewing. 'I'his may be accomplished by making the threads of greater pitch so that, when the string is rotated in the oppositedrction, it will unscrew at the back-off joint. The casing is extended out of the hole by the use of special semi-flush Joints for drilling strings, and a valve joint 2i is inserted in the string. The top of the casing string is connected to a swivel 22 by a hammer joint 23. No kelly is used. In drilling, a special drive arrangement for round drill pipe is used. 'I'his is known to the art. 'Ihe drive consists principally of a drill pipe clamp in which four tong guides are set. The grip on the pipe is secured by driving wedges through slotted pins. In drilling, the clamps travel downwardon two upright drive posts set at opposite points in the rotary table. The length of the drive is fixed and when this amount has been drilled, the rotation is stopped and the wedges sledged loose, the clamps lifted to the tops of the'drive posts and drilling is continued and the operation repeated.

Figure 2 shows the assembly after the drilling has progressed through the heaving shale to the point where-it is necessary to add a new section. While the drilling is proceeding, oil well mud which contains silicates is pumped from the mud pit 24 by pump 25 through hose 26 which is controlled by valve 21 to the swivel connection whence the mud passes downwardly through the pipe, and out of the casing through pipe 28 back into the mud pit. When the point of drilling is reached when it is necessary to add a new section of drill string as shown in Figure 2, the plug 29 of the valve union shown in Figure 9 is unscrewed and the hose 29' is screwed into the seat. Valve 30 is then opened and mud will be pumped through hose 29' moving valve 1 upwardly on its seat, and circulation will be continued through the opening in the side of the union. Valve `21 is then closed and the wedge pins I4 of the quick acting joint are removed. Connection with the top of a new section of drilling string is then made to the swivel and the new section hoisted in the derrick and the lower end likewise connected by a quick acting joint. Valve 21 is then opened and valve 30 is then closed, circulation now continuing through the new section of the assembly. Each new section has near the top thereof a valve union. When the hose is removed from the valve union the valve 'l will close the opening and the plug 29 is replaced to prevent the valve from accidentally stopping the iiow or becoming unseated. Drilling is continued until the heaving shale has been penetrated. This is shown diagrammatically in Figure 4. A fishing tool is then inserted for drawing the wire line collapsible bit from the hole. The fishing tool is inserted through a stufling box, circula tion being maintained continuously. The bit is withdrawn from the hole and the drilling string is then cemented since it is to act as a casing. It will be observed that the drilling string is not withdrawn from the hole for the setting of casing but that casing is set simultaneously while the drilling proceeds, the drilling pipe itself being casing. It will be observed by reference to Figure 4 that a number of valve unions 2| and a.

number of quick acting joints 23 will be in the hole. The valve unions involve a restricted cross sectional opening and the valve unions and quick acting joints are expensive. It will be undesirable to leave these in the hole as permanent parts of the casing of the well.

After the drill casing has been cemented, the entire string is rotated in the opposite direction and the drill string will unscrew at the back-a' joint since this is designed for this purpose. Since the back-off joint is above the bottom of the casing at least a distance equal to the thickness of the heaving shale, it will be observed that the entire region of heaving shale is protected by a casing. All of the valve unions and quick acting joints will be recovered'by the use of the back-oli joint. A casing having the customary joints and terminating in a back-ofi' joint connection and being of full cross sectional area is *gmbh stage of the-drilling,'" casingljclar through the heaving Ishale,securely cementedA inf place and from`v this point' conv `rational,drilling methods may be* ai employed 'theloil sands are reached. e@ inclifcasing' kIl which has been cementeigat'flhadjadepth'of about 8021 feet. The ugunngtprocededin .the conventional manner and" a`5%"inch" casing 34 was run to a depth of 9083 feet and cemented. 'Ihe casing I 9 through the heaving shale formations supports the heaving shale and prevents it from caving. The sloughing which inevitably occurs when drlllingthrough heaving shale is not oi such magnitude as to enable serious heaves to occur. 'I'he shale packs around the casing and becomes static and the danger of loss of the hole is thus averted.

From the foregoing description, it is believed that my method of drilling will be clear to those skilled in the art. It will be observed that I have accomplished the objects of my invention. By my method, heaving shale formations can be-penetrated where drilling has repeatedly been attempted unsuccessfully.

It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. 'Ihis is contemplated by and is Within the scope of my claims. It is further obvious that various changes may be made in details Within the scope of my claims without departing from the spirit of my invention. It is,

therefore, to be understood that my invention is not to be limited to the specific details shown and described. i

Having thus described my invention, what I claim is:

1. A method of drillingoil and gas wells into the earth through a subterranean formation of caving nature, including the steps of drilling in a conventional manner until a region in the vicinity of the caving formation is reached. withdrawing the drilling string, setting a casing in the hole thus formed, continuing the drilling through the casing While maintaining continuous circulation of a drilling mud containing a silicate, adding sections of drilling pipe to the drilling string as drilling proceeds, while maintaining continuous circulation of said drilling mud until the caving formation has been penetrated, converting the drilling pipe into a well casing without removing the same from the drill hole and then continuing the drilling until the desired objective is reached.

2. An assembly for drilling through heaving shale comprising in combination the following assembly; a bit head adapted to receive a removable bit, a plurality of sections of drill pipe ceupled to each other, an easily uncoupled joint, further sections of drill pipe coupled to said rst sections of drill pipe by said easily detachable joint and coupled to each other by conventional joints, a union having an opening in the side thereof and provided with a valve adapted to close the bore of said union or said opening in the side thereof, said union coupling a further section of drill pipe to the remainder of the assembly, said last named section of drill pipe being provided with a quick acting coupling means, a swivel coupled to the assembly through said quick acting coupling means, means for pumping an oil well mud into said swivel for passage down the drilling assembly, means for pumping oil well mud through said 75 valve union (or passage down said drilling assembly, vsaid easily uncoupled joint being positioned above th bit head a distance approximately equal to the thickness oi the heaving shale to be penetrated.y f

3. A method of drilling oil and gas wellsv into f the earth through a subterranean formation oi' caving nature,y including the steps ot drilling in a conventional manner until a' region in the vicinity of the caving formation is reached, withdrawing the drilling string, setting a casing in the hole thus formed, continuing the drilling through the casing lwhile maintaining continuous circulation of afdrilllngmuddding sections of drilling pipe to the drilling stringy as drilling proceeds. while maintaining continuous circulation ot said drilling ymud until the caving formation has been penetrated,converting the drilling pipe into a well y casing without removing the same from the drill vhole and thenvcontinuing the drilling until the desired objective 'is reached.' v

JOSEPH G. DYER. 

